I second what Semisane mentioned, try shooting sticks if you haven't already. I'm the limiting factor when it comes to shooting accuracy with all of my firearms. I carry a set of sticks most all of the time to give myself an edge, and they help, but you should definitely practice with them. A 100 yard shot with a rest of some sort is a waybetter proposition than the same shot offhand, at least with my shooting skill anyway.

An aperture sight helps me a bunch too. In the end, burning plenty of powder consistently through the summer and not just off the shooting bench is probably the real key to consistent shooting at any distance.